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Resolves: 456572

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This commit is contained in:
Neil Horman 2008-07-28 11:26:50 +00:00
parent 99ee15683c
commit fcd8cdc811
2 changed files with 23 additions and 26 deletions
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44
kexec-kdump-howto.txt
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@ -470,30 +470,24 @@ kexec. Note that the kdump kernel should still be able to create a dump,
and when the system reboots, video should be restored to normal.
Notes on RHEL5 configuration:
The RHEL5 kexec-utils package contains two extra configuration files:
/etc/sysconfig/kdump
This file allows you to specify an alternate kernel to boot in the
event of a panic (other than the kernel running at the moment), and allows you
to override or append options on the kernel command line. It also alows you
to pass extra options to the kexec utility when the kdump service is starting.
See documentation in the template kdump sysconfig file for exact usage
/etc/kdump.conf
This file allows you to configure how kdump will record your core
file. Unlike the stock version of kdump, the RHEL5 version of kdump attempts
to record your vmcore file from the initramfs, so as to still function
properly in the event that your root file system is corrupted and unmountable.
This file is interrogated on kdump service start and is used to populate the
initramfs for the kdump kernel with the appropriate data and utilities to copy
your core file to the desired location. See documentation in /etc/kdump.conf
for available config directives and targets. Note especially the ifc option.
kdump will attempt to determine which network interface to use when dumping to
a remote server, but due to the possibility of interface renaming, or alternate
module load strategies, the interface name may change in the kdump kernel.
This option is used to override that guess, so that the appropriate interface
will be activated in the kdump kernel.
Notes on resetting video:
Video is a notoriously difficult issue with kexec. Video cards contain ROM code
that controls their initial configuration and setup. This code is nominally
accessed and executed from the Bios, and otherwise not safely executable. Since
the purpose of kexec is to reboot the system without re-executing the Bios, it
is rather difficult if not impossible to reset video cards with kexec. The
result is, that if a system crashes while running in a graphical mode (i.e.
running X), the screen may appear to become 'frozen' while the dump capture is
taking place. A serial console will of course reveal that the system is
operating and capturing a vmcore image, but a casual observer will see the
system as hung until the dump completes and a true reboot is executed.
There are two possiblilties to work around this issue. One is by adding
--reset-vga to the kexec command line options in /etc/sysconfig/kdump. This
tells kdump to write some reasonable default values to the video card register
file, in the hopes of returning it to a text mode such that boot messages are
visible on the screen. It does not work with all video cards however.
Secondly, it may be worth trying to add vga15fb.ko to the extra_modules list in
/etc/kdump.conf. This will attempt to use the video card in framebuffer mode,
which can blank the screen prior to the start of a dump capture.

5
kexec-tools.spec
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@ -1,6 +1,6 @@
Name: kexec-tools
Version: 1.102pre
Release: 13%{?dist}
Release: 14%{?dist}
License: GPL
Group: Applications/System
Summary: The kexec/kdump userspace component.
@ -265,6 +265,9 @@ done
%changelog
* Mon Jul 28 2008 Neil Horman <nhorman@redhat.com> - 1.102pre-14
- Add video reset section to docs (bz 456572)
* Mon Jul 11 2008 Neil Horman <nhorman@redhat.com> - 1.102pre-13
- Fix mkdumprd to support dynamic busybox (bz 443878)